Trailers of various sizes and forms, e.g., box trailers, covered vans, boat trailers, mobile homes, etc., are connected behind various types of automotive trailer-towing vehicles, e.g., tractors, small trucks, recreational vehicles, and automobiles. Governmental regulations require that such trailers be provided with lighting systems similar to those required on the trailer-towing vehicle, namely, running lights to illuminate the trailer for night operation as well as special lighting for both day and night use to indicate the direction of intended turns as well as the application of brakes. The electrical connection between the towing vehicle and the trailer is made by means of appropriate cables connected by mating male/female plugs.
In order to assure that the lights of the trailer respond appropriately to the lighting signals initiated by the driver of the trailer-towing vehicle, testing of the interconnection of the two lighting systems is necessary. Normally, such testing requires two people, namely, one person to initiate the various light signals in sequence from the towing vehicle and a second person to view the lights of the trailer and towing vehicle to determine whether or not the operation of the two lighting systems is in correct correspondence. If a second person is not available, a lone individual must first initiate the lighting signals from the driver's seat of the towing vehicle one at a time, getting out of the towing vehicle and moving behind the vehicle and trailer to check the proper operation of each signal. While this latter method is particularly time-consuming, it is also extremely difficult to test the operation of the braking lights, since a means must be devised to hold down the brake pedal of the towing vehicle when the lone tester leaves the driver's seat and moves back to check the operation of the lights that must properly indicate each application of the towing vehicle's brakes.
Therefore, in recognition of this problem and its important relation to highway safety, many different testing arrangements have been devised to determine the proper operation of such automotive trailer light systems. All such prior art testing apparatus known to me is relatively complex and expensive. Most prior art devices include a plurality of switches and test lights, one respective switch and one respective test light for each of the separate lighting control circuits, and some known testers even include "flasher" units for activating the lamps used for directional indications. My tester is much less expensive and simpler to make and easier to operate.